Amphiphilic compounds are compounds with hydrophilic (water-loving) and hydrophobic (water-fearing) regions. When dispersed in water at a concentration above their critical micelle concentration or “CMC,” amphiphilic compounds spontaneously self-associate into micelles. Micelles have a size which depends on properties of the solvent in which they are dispersed. The size of micelles can vary from approximately two to several hundreds of nanometers in equivalent spherical diameter.
When a drug is an amphiphilic compound which forms micelles when formulated for intravenous administration, the pharmacokinetics of the drug can depend upon the size of the micelle formed. Pharmacokinetics describes the time course of the distribution of a drug within the body after administration. The pharmacokinetics of a drug can affect its efficacy, metabolism, distribution, and/or toxicity in the body, either positively or negatively. For other routes of administration, micelle size can also influence pharmacokinetics. When the drug is in the form of a micelle, the effectiveness of delivery of the drug to the site of action depends upon the size of the aggregate, as the micelle size might affect diffusion, transport across cell membranes, and interactions with enzymes, transport proteins and lipids.
Prior to the work of the present inventors, the micelle size of amphiphilic drug compounds in water was known to be governed by the state of the solution, so once the formulation of the drug was chosen, a predetermined micelle size distribution was expected to result. The ability to control the micelle size of a drug delivered in a pharmaceutical formulation was severely limited, and control of the rate of delivery of drug to the site of action, therefore, was limited due to the inability to control the size of the micelle in solutions.
There is a need in the art to control or fix the size of micelles formed by amphiphilic drug compounds in aqueous solutions so that drug delivery rates and pharmacokinetics can be controlled. The present invention is directed to these, as well as other, important ends.